"Kupiłaś nową sukienkę?"

Translation: Did you buy a new dress?

[tgbarnett]

... A new dress

[deactivated user]

I dont think the problem is with 'have you bought' or 'did you buy' the problem is with the use of 'the' it should be in 'a' new dress regardless of how you phrase the first part of the question

[brian995925]

Had you bought a new dress is not correct. It is not a question. Had you bought a new dress you could wear it. This would be correct.

[Jellei]

Seeing Trofaste's answer, I'm keeping it, but it will not be a suggested option anymore, just an accepted one.

[Trofaste]

That's certainly a correct sentence, but "Had you bought a new dress?" is correct as a question too. Remember it's past tense, not present tense. You can say "You had bought a new dress before going to the party", then just turn it around to make it a question, "Had you bought a new dress before going to the party?" Make sense?

[alik1989]

Why do they offer past perfect here?

[immery]

Do you mean :

• you had multiple choice, and past perfect was one of them. While we used to have equivalent of past perfect, we do not use it any more, we use past tense for things that happened before other past things.

• why is the lesson called past perfect? It's misleading, it should be past tense of perfective verbs or sth like that.

[alik1989]

Strange... There were words to rearrange into a sentence and as far as I remember they offered 'had' and 'bought'

[immery]

Did you buy a new dress?

Have you bought a new dress?

Had you bought a new dress?

are valid translations depending on context.

I think I would go with Have you bought a new dress? as my first assumption.